CN1674102A - Magnetic recording medium, method for manufacturing recording medium and magnetic recording apparatus - Google Patents

Abstract

Provided are a magnetic recording medium, a method for manufacturing the recording medium, and a magnetic recording device. A magnetic recording layer is formed on the underlayer including the Cu crystal grain layer and the deposited nitrogen atom layer on the surface of the Cu crystal grain layer. A magnetic recording layer having a very small average grain diameter and a very narrow grain diameter distribution is thereby obtained. A magnetic recording medium including the above-mentioned magnetic recording layer exhibits excellent signal-to-noise ratio characteristics under high-density recording conditions.

Description

Magnetic recording medium, recording medium manufacturing method, and magnetic recording device

Cross References to Related Applications

This application is based on and claims priority from prior Japanese Patent Application No. 2004-090669 filed on March 25, 2004, the entire contents of which are incorporated herein by reference.

technical field

The present invention relates to a magnetic recording medium, a method for manufacturing the recording medium, and a magnetic recording device, and more particularly, to a magnetic recording medium having a high recording density, a method for manufacturing such a recording medium, and a hard disk drive such as a high-density recording medium equipped therein Isomagnetic recording device.

Background technique

As a magnetic recording system for recording and reproducing information, the application fields of hard disk drives (HDDs) have been expanded from the original computer-related application fields to various other application fields such as home video recorders and car navigation systems. In addition to having a higher recording capacity and lower cost, the application field of the hard disk drive has been expanded due to its advantages such as high data access speed and high data storage reliability. As the field of application of HDDs expands, the demand for HDDs with greater recording capacity is increasing. In order to meet such demands, large-capacity recording technologies have been developed by increasing the recording density of magnetic recording media.

As the recording density of the magnetic recording medium of the HDD increases, the recording bit size and the diameter of the magnetization inversion unit become extremely small. As a result, the phenomenon of thermal drop in recording signal magnetization and recording and reproducing performance due to the thermal fluctuation effect caused by the small-sized magnetization inversion unit becomes conspicuous. Furthermore, as the size of recording bits is reduced to a sufficiently small size, noise signals appearing in boundary regions between recording bits become larger, and the noise becomes to have a greater influence on the signal-to-noise ratio. Therefore, in order to obtain a higher recording density, it is necessary to stabilize the thermal stability of the magnetization of the recording signal on the one hand, and to obtain lower noise characteristics under the condition of a higher recording density on the other hand.

In order to reduce noise in magnetic recording media, the size of magnetic crystal grains constituting a recording layer has heretofore been made smaller. For example, non-magnetic Cr is precipitated by adding a small amount of Ta or B (see Japanese Patent Application Publication No. 11-154321 and 2003-338029), and by heat treatment at an appropriate temperature (see Japanese Patent Application Publication No. Hei 3-235218 and Hei 6-259764), the magnetic crystal grains of the Co-Cr magnetic layer of the widely used magnetic recording medium are made into a very small size. Recently, a method for obtaining a magnetic recording layer having a so-called granular structure obtained by adding an oxide such as SiOx to the magnetic layer is employed. In the magnetic layer of this granular structure, non-magnetic grain boundary material surrounds magnetic crystal grains (see Japanese Patent Application Publication Nos. Hei 10-92637 and 2001-56922).

However, these methods cannot control the crystal grains of the magnetic layer and the under layer by going back to the nucleation stage of the crystal grains of the under layer and the magnetic recording layer. These methods control the average magnetic grain diameter and grain boundary region only by selecting the combination of raw materials, the composition of the raw materials or by selecting the deposition conditions. When trying to reduce the diameter of the grains in the underlayer to a smaller size, the crystallization quality and grain orientation of the grains in the underlayer will be reduced, and the decrease in the crystalline quality of the underlayer grains will have a negative impact on the magnetic crystal grains. affect particle formation.

In fact, it has been found that magnetic layers prepared in this way have a wide distribution of grain size and grain boundary width. The magnetic recording medium in which the average grain size of the magnetic crystal grains was reduced to 5 nm exhibited poor thermal fluctuation durability. The proportion of very small diameter grains unstable to thermal fluctuations is high. Therefore, it is difficult to obtain a higher recording density by this method.

Contents of the invention

In order to obtain a magnetic recording medium with high recording density, it is necessary to obtain recording magnetization stability not affected by thermal fluctuations and to obtain low noise performance under high recording density conditions. Then, to obtain a higher recording density, two problems need to be solved. One problem to be solved is to obtain low noise performance by reducing the average diameter of magnetic crystal grains in the magnetic layer. Another problem to be solved is to obtain thermal stability by obtaining a smaller grain size distribution of magnetic grains that does not contain too small grains susceptible to thermal fluctuations.

The inventors of the present invention have made important discoveries as a result of long-term search work for solutions to these problems. The finding is that when the underlayer is a Cu metal film with a thin deposited layer of nitrogen atoms, the resulting magnetic layer can have a small magnetic grain size and a very narrow grain size distribution. After conducting further studies, the inventors solved the above-mentioned problems and completed the present invention.

The magnetic recording medium of the present invention includes a substrate, an underlayer formed on the substrate, a magnetic recording layer on the underlayer, and a protective layer formed on the magnetic recording layer. The underlayer includes a grain diameter controlling underlayer containing Cu crystal grains and a deposition layer of nitrogen atoms formed on the grain diameter controlling underlayer.

The manufacture method of the magnetic recording medium of the present invention comprises the steps of: forming a grain diameter control cushion layer containing Cu crystal grains on a substrate, forming a deposition layer of nitrogen atoms depositing nitrogen on the surface of the grain diameter control cushion layer , and a magnetic recording layer is formed on the substrate having the nitrogen layer deposited on the grain diameter control underlayer.

And, the magnetic recording and reproducing apparatus of the present invention includes: the above-mentioned magnetic recording medium, a recording medium drive mechanism for driving the magnetic recording medium, a recording and reproducing mechanism for recording information on the magnetic recording medium and reproducing information from the magnetic recording medium. A reproducing head mechanism, a head driving mechanism for driving recording and reproducing heads, and a recording and reproducing signal processing system for processing recording signals and reproducing signals.

In the present invention, the grain size of Cu of the under layer grains does not need to be small. The problems encountered in the prior art methods of obtaining small magnetic grains using a small grain size underlayer can thus be avoided, so that a recording medium having improved recording and reproducing characteristics can be obtained according to the present invention. The grain diameter controlling underlayer containing Cu crystal grains of the present invention may contain other elements capable of exerting the advantages of the present invention.

At present, the detailed mechanism of obtaining small-sized grains by depositing a Cu metal film underlayer by using nitrogen is unclear. Here, two articles will be introduced and a simple comparison will be made between the present invention and the two articles.

In an article appearing in Surface Science, Vol. 523, pp. 189-198 (2003), an alternately configured surface structure consisting of regions with nitrogen adsorption and regions without adsorption is reported. Nitrogen atoms were adsorbed on the surface of bulk single crystal Cu after purification treatment under ultra-vacuum of 10 ^-9 Pa.

In another article appearing in Material Science and Engineering, Vol. B96, pp. 169-177 (2002), the ordered arrangement of nitrogen atoms on the surface of single crystal Cu is explained. The ordered arrangement is interpreted as a self-organized structure due to stress interactions arising on the clean surface of bulk Cu single crystals.

Comparing these two articles with the present invention, it can be seen that the grain diameter control underlayer containing Cu crystal grains in the present invention is not a bulk single crystal but a thin film. Thus, the thin films in the present invention have a stress regime quite different from the surface of bulk Cu single crystals in these articles. Thus, the reoriented ordered surface structures of these articles cannot always be expected for the films of the invention. At present, the mechanism by which the present invention is used to obtain the small grain size is unclear. Discovering the mechanism of the present invention is an important problem to be solved. According to the present invention, the magnetic grains of the magnetic layer produced can be very small, and a magnetic recording medium with improved signal-to-noise ratio and high-density recording can be obtained.

Description of drawings

FIG. 1 is a schematic cross-sectional view of a magnetic recording medium according to an embodiment of the present invention.

2 is a schematic cross-sectional view of a magnetic recording medium including an orientation control underlayer for controlling the orientation of Cu grains between a substrate and a grain diameter control underlayer according to an embodiment of the present invention.

3 is a schematic in-plane view of a magnetic recording layer for a magnetic recording medium showing magnetic crystal grains arranged in a tetragonal lattice structure according to an embodiment of the present invention.

Fig. 4 is a schematic example of a ring pattern of a reciprocal lattice of a tetragonal lattice structure.

5 is a schematic cross-sectional view of a magnetic recording medium having an underlayer according to an embodiment of the present invention.

6 is a schematic cross-sectional view of a magnetic recording medium having a soft magnetic underlayer according to an embodiment of the present invention.

7 is a cross-sectional view of a magnetic recording medium having a bias layer for a soft magnetic underlayer according to an embodiment of the present invention.

FIG. 8 is a schematic oblique view of the magnetic recording apparatus according to the embodiment of the present invention for explaining its configuration by partially removing the cover.

FIG. 9 shows the relationship between the number of deposited nitrogen atoms per unit area and the average crystal grain diameter of the magnetic recording layer in Example 1. FIG.

FIG. 10 shows the relationship between the average diameter of Cu crystal grains and the average diameter of magnetic crystal grains in the magnetic recording layer.

11 shows the relationship between the number of magnetic crystal grains per unit area of the magnetic recording layer of Example 1 and the signal-to-noise ratio (SNR _m ) of the differential waveform of the magnetic recording layer.

Detailed ways

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic cross-sectional view of a magnetic recording medium according to an embodiment of the present invention. In FIG. 1 , on a substrate 11 , a Cu thin film cushion layer 12 a for grain diameter control is provided. A deposition layer 12b of nitrogen atoms is formed on the diameter control pad layer 12a. A magnetic recording layer 14 is formed on the deposited layer 12b of nitrogen atoms, and a protective and lubricating layer 15 is formed on the magnetic recording layer 14.

If represented by the average number of atoms per unit area, the number of deposited nitrogen atoms per unit area required for the deposition layer 12b of nitrogen atoms on the surface of the crystal grain diameter control pad layer 12a is 1×10 ¹³ to 1×10 ¹⁵ atoms/cm ² . When the amount is less than 1×10 ¹³ atoms/cm ² , no significant effect of reducing the average grain diameter can be produced on the magnetic recording layer. Also, experimental results show that when the number is greater than 1×10 ¹⁵ atoms/cm ² , the degree of magnetic grain orientation of the magnetic recording layer decreases. The number of deposited nitrogen atoms is preferably 5×10 ¹³ to 5×10 ¹⁴ atoms/cm ² .

The amount of nitrogen atoms on the deposited layer 12b of nitrogen atoms can be estimated by secondary ion mass spectrometry (SIMS). To estimate the number of nitrogen atoms, nuclear reaction analysis (NRA) using H ⁺ or ¹² C, Rutherford backscattering, X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), etc. method. Also, for such estimation, the atom probe method described in Applied Physics Letters, Vol. 69, pp. 3095-3097 can also be used.

As a method for depositing nitrogen atoms on the surface of the grain diameter controlling under layer 12a, a method of exposing the grain diameter controlling under layer 12a after depositing nitrogen atoms or nitrogen atom groups can be used. Other methods such as irradiating nitrogen ions to reach the grain diameter controlling under layer 12a or sputtering the Cu surface in a nitrogen atmosphere may also be used. And, a method of exposing the surface to _NH4 atmosphere and then removing H can be used.

The Cu crystal grains required for the grain diameter control under layer 12a have a wide flat surface for obtaining the magnetic recording layer 14 with good crystallinity. Therefore, Cu grains are required to have a larger average grain diameter. The desired average grain diameter of the Cu crystal grains is 50 nm or more, and the diameter is preferably 100 nm or more. A single crystal film having no grain boundaries is more preferable. When the Cu film is not smooth to some extent, the film can be obtained if the film has a larger portion of the stepped surface forming the film surface.

Since a high degree of magnetic grain orientation can be obtained in the magnetic recording layer 14, the grain diameter control under layer 12a in which the orientation of the same crystal plane of each Cu crystal grain is parallel to the same plane is required. To obtain very small magnetic crystal grains in the magnetic recording layer 14, a grain diameter control underlayer in which each (100) plane of each Cu crystal grain is oriented parallel to the substrate surface is particularly required.

As shown in FIG. 2, an orientation control underlayer 12c for increasing the (100) plane orientation of Cu crystal grains in the grain diameter control underlayer 12a can be provided between the substrate 11 and the grain diameter control underlayer 12a . As the orientation control under layer 12c, at least one material selected from NiAl, MnAl, MgO, NiO, TiN, Si, and Ge can be used. The orientation control under layer 12c need not be provided directly adjacent to the grain diameter control under layer 12a, but may be provided through an intermediate layer.

Each Cu crystal grain of the grain diameter control layer 12 a forms a plurality of magnetic crystal grains in the magnetic recording layer 14 on average. To obtain a large reproduction output of recording signals, the required average areal density of magnetic crystal grains in the magnetic recording layer 14 is 1×10 ¹² to 8×10 ¹² crystal grains/cm ² . When the average areal density of the magnetic crystal grains is less than 1×10 ¹² grains/cm ² , the SNR decreases. SNR also decreases when the average areal density is higher than 8×10 ¹² grains/cm ² .

From the experimental results of the inventors of the present invention, it can be seen that when the magnetic crystal grains are substantially arranged in an ordered structure of a tetragonal lattice, the noise level of the recording and reproducing characteristics can be greatly reduced and made satisfactory.

FIG. 3 is a schematic in-plane structure of a magnetic recording medium according to an embodiment of the present invention. White objects represent magnetic grains 1 . The presence of the tetragonal lattice structure arrangement of the magnetic crystal grains 1 can be confirmed by image processing and analyzing a transmission electron microscope (TEM) image of the film surface of the magnetic recording layer 14 .

)。可以通过对磁记录层使用低能电子衍射并对衍射图案进行分析，进行类似的评价。Using image processing and analysis software, spectra can be obtained as a result of fast Fourier transformation of the binary image obtained by increasing the image contrast of the magnetic grain and grain boundary regions. When essentially the pattern shown in Figure 4 can be found in the spectrum, the magnetic grains can be considered as an arrangement with a tetragonal lattice structure. In fact, the ratio of the distances of the two types of periodic points or rings to the center is 1:1/ (R ₁ and

). Similar evaluation can be performed by using low-energy electron diffraction on the magnetic recording layer and analyzing the diffraction pattern.

For the magnetic recording medium of the present invention, the magnetic recording layer 14 having a granular structure is required. The granular structure having the non-magnetic grain boundary region in the magnetic recording layer 14 leads to a reduction in exchange interaction between magnetic crystal grains, and to a marked reduction in transition noise of recording and reproducing characteristics.

Disordered alloys such as Co-Cr and Co-Pt, ordered alloys such as Fe-Pt, Co-Pt and Fe-Pd, and multilayer films such as Co/Pt and Co/Pd are required as the magnetic recording layer 14. s material. These alloys and multilayer films are desired because of their higher crystalline anisotropy energy and thus higher thermal swing durability. The magnetic properties of these alloys and multilayers can be improved by adding additional elements such as Cu, B, and Cr, if desired. CoCrPt, CoCrPtB, CoCrPtTa, CoCrPtNd, CoCrPtCu, and FePtCu alloys can also be used as the material of the magnetic recording layer 14 .

As a material for forming the grain boundary region of the granular structure, compounds such as oxides and carbides are required because these compounds do not form a solid solution with the above-mentioned magnetic grain-forming materials and are easily separated. Compounds forming grain boundary regions include compounds such as _SiOx , _TiOx , _CrOx , _AlOx , _MgOx , _TaOx , _SiCx , _TiCx , and _TaCx .

The magnetic recording layer 14 may have a double-layer structure or a multi-layer structure. In this case, at least one layer of these two-layer or multi-layer structures has the above-mentioned structure.

As shown in FIG. 5, an intermediate pad layer 12d for controlling the characteristics of the magnetic recording layer 14 may be provided in addition to the grain diameter control pad layer 12a and the deposited nitrogen layer 12b and orientation control pad layer 12c.

By using the granular structure layer as the intermediate cushion layer 12d, the degree of crystal orientation can be improved. In addition to a smaller average grain size and a smaller grain diameter distribution, an improvement in the degree of crystal orientation can also improve recording and reproduction characteristics.

As the non-magnetic crystal material of the intermediate pad layer 12d having a granular structure, Pt, Pd, Ir, Ag, Cu, Ru, and Rh can be cited. These metallic materials are required because they have good lattice compatibility with the aforementioned magnetic crystal grains and can improve the degree of crystal orientation.

Compounds such as oxides and carbides are required as materials for forming the grain boundary region of the intermediate pad layer 12d. These compounds are used as the material for forming the grain boundary region because these compounds do not form a eutectic solution with the above-mentioned nonmagnetic crystal grain-forming material and are easily separated. Compounds forming grain boundary regions include compounds such as _SiOx , _TiOx , _CrOx , _AlOx , _MgOx , _TaOx , _SiCx , _TiCx , and _TaCx . When the underlayer is not magnetic as a whole, the material constituting the underlayer may contain a magnetic metal.

The intermediate cushion layer 12d having a granular structure may be constituted as a multilayer of two or more layers. This layer need not be provided adjacent to the magnetic recording layer 14 .

When a soft magnetic underlayer 16 is provided between each underlayer and the substrate 11 as shown in FIG. 6, the magnetic recording medium of the present invention is used as a perpendicular magnetic recording medium.

The soft magnetic backing layer 16 may be provided in the above-mentioned magnetic recording medium of the so-called perpendicular dual-layer medium including the magnetic recording layer 14 provided on the soft magnetic layer 16 . The soft magnetic backing layer 16 shares part of the function of the magnetic head by returning the magnetic flux generated by the recording magnetic field from the monopolar magnetic head, across the magnetic recording medium horizontally, and back to the magnetic head. Therefore, the soft magnetic backing layer 16 provided in the magnetic recording medium has the function of providing the magnetic recording layer 14 with a steep vertical magnetic field with sufficient amplitude.

Examples of the soft magnetic underlayer 16 include CoZrNb, FeSiAl, FeTaC, CoTaC, NiFe, Fe, FeCoB, FeCoN, and FeTaN.

As shown in FIG. 7, a bias layer 17, for example substantially comprising a hard in-plane magnet layer and an antiferromagnetic material layer, may be disposed between the soft magnetic backing layer 16 and the substrate 11. Magnetic domains are easily formed in the soft magnetic underlayer 16, and the magnetic domains cause peak-like noise. By applying a magnetic field in the radial direction of the bias layer 17 and applying a bias field to the soft magnetic underlayer 16 provided on the bias layer 17, the formation of magnetic domains can be avoided. To avoid the formation of larger magnetic domains, the bias layer can be a multilayer structure with a diffuse anisotropic field.

Examples of the material constituting the bias layer 17 include CoCrPt, CoCrPtB, CoCrPtTa, CoCrPtTaNd, CoSm, CoPt, FePt, CoPtO, CoPtCrO, CoPt-SiO ₂ , CoCrPt-SiO ₂ and CoCrPtO-SiO ₂ .

As shown in FIGS. 6 and 7 , in order to improve the (100) plane crystal orientation degree of the Cu crystal grains of the crystal grains, the above-mentioned orientation control layer 12 c may be provided.

A glass substrate, an Al alloy substrate having an oxide surface or a Si single crystal substrate, a ceramic substrate, and a plastic substrate can be used as the substrate 11 . Also, an inorganic substrate plated with NiP, for example, can be used.

A protective layer 15 may be formed on the magnetic recording layer 14 . As the protective layer 15, graphite or diamond-like carbon can be used. Examples of the protective layer material include other materials such as _SiNx , _SiOx , and _CNx .

As a method of depositing the above-mentioned layers, a vacuum vapor method, various sputtering methods, molecular beam epitaxy, ion beam vapor method, laser ablation method, and chemical vapor deposition method can be used.

FIG. 8 is a schematic oblique view of the magnetic recording apparatus according to the embodiment of the present invention for explaining its configuration by partially removing the cover.

In FIG. 8, a magnetic disk 81 according to the present invention is fixed on a spindle 82 and driven at a constant speed by a spindle motor not shown in the figure. At the tip of a suspension beam 84 composed of two thin-plate-shaped leaf springs, a slider 83 for carrying a recording head for recording information and an MR head for reproducing recorded information contacting the surface of the magnetic disk 81 is fixed. The cantilever 84 is connected to one side of a cantilever arm 85 having a bobbin accommodating a driving coil not shown in the figure.

On the other side of the cantilever arm 85, a voice coil motor 86 is provided, which is a kind of linear motor. The voice coil motor 86 is constituted by a magnetic circuit including a drive coil wound onto a bobbin of the cantilever arm 85 , a permanent magnet and an opposing yoke.

The cantilever arm 85 is supported by ball bearings not shown in the figure, and is driven by a voice coil motor 86 to generate cyclic swinging motion. The position of the slider 83 on the magnetic disk 81 is controlled by a voice coil motor 86 . In Fig. 8, a portion of the cover 88 is shown.

Hereinafter, examples of the present invention for explaining the present invention will be further described in detail.

(Example 1)

Put the non-magnetic 2.5-inch glass substrate into the vacuum chamber of the c-3010 type sputtering device of ANELVA company.

The vacuum chamber of the sputtering apparatus was evacuated to 1×10 ^-6 Pa or lower. The substrate was then heated to about 300°C using an infrared heater. The temperature of the substrate was kept at about 300°C, a CoZrNb film was deposited to a thickness of 200 nm as a soft magnetic underlayer, and then a Cu film was deposited to a thickness of about 30 nm. Then the temperature of the substrate was raised to about 500° C., and nitrogen ions were irradiated onto the surface of the Cu film in a nitrogen atmosphere of 0.1 Pa using an ion gun of 200 eV. After nitrogen ion irradiation, a 5 nm thick Fe ₅₀ Pt ₅₀ film was deposited.

A carbon film was then deposited to a thickness of 5 nm. To deposit CoZrNb film, Cu film, Fe ₅₀ Pt ₅₀ film and C film, the argon gas pressure is 0.7 Pa, 0.7 Pa, 5 Pa and 0.7 Pa respectively, and the targets are CoZrNb, Cu, Fe ₅₀ Pt ₅₀ and C respectively. Sputtering was performed using DC sputtering.

For CoZrNb, Fe ₅₀ Pt ₅₀ and C deposition, the power input to the target was fixed at 1000W, while for Cu deposition, the power was varied in the range of 100-1000W.

Magnetic recording media with Co ₅₀ Pt ₅₀ , Fe ₅₀ Pd ₅₀ , Co ₇₀ Cr ₁₀ Pt ₁₀ instead of Fe ₅₀ Pt ₅₀ were fabricated using essentially the same procedure as described above. By selecting the ion irradiation time, the amount of nitrogen deposition deposited on the surface of the Cu film is controlled. By changing the power input to the target, the crystal grain diameter of the Cu film is changed.

After the deposition was completed, each protective layer was coated with a perfluoropolyether (PFPE) lubricant about 1.3 nm thick by dip coating. Then, each magnetic recording medium sample was obtained.

As a comparative example, a conventional perpendicular magnetic recording medium was prepared through the following steps. A non-magnetic 2.5-inch glass substrate was placed in a vacuum chamber of a sputtering apparatus, and the vacuum chamber was evacuated to 1×10 ^-6 Pa or lower. After heating the substrates to about 300°C with an infrared heater, a 200-nm-thick CoZrNb film as a soft magnetic pad layer, a 10-nm-thick Ta film as a seed-layer, and a 10-nm-thick Ta film as a pad layer were deposited on each substrate. A 20nm thick Ru film, a 15nm thick Co ₆₅ -Cr ₂₀ -Pt ₁₄ -Ta ₁ layer as a magnetic recording layer, and a 5 nm thick protective layer, and the lubricant was applied using the same procedure as in the above example. To deposit CoZrNb film, Ta film, Ru film and CoCrPtTa film, the argon gas pressure is 0.7 Pa, 0.7 Pa, 0.7 Pa, 5 Pa and 0.7 Pa respectively, and the targets are CoZrNb, Ta, Ru, Co ₆₅ Cr ₂₀ Pt ₁₄ Ta ₁ floor. Sputtering was performed using DC sputtering. The power input to the target was fixed at 1000W.

The microstructure, grain diameter, and grain size distribution of each fabricated sample were confirmed by a transmission electron microscope (TEM) at an accelerating voltage of 400 kV. Using NRA using H ⁺ and SIMS using Cs ⁺ similar to the method reported in Surface Science (Surface Science) Vol. quantity.

The recording and reproducing characteristics (reading and writing characteristics, R/W characteristics) of each magnetic recording medium were evaluated using a turntable. The applied magnetic head is a combination of a 0.3 μm track width unipolar head and a 0.2 μm track width MR head.

The measurement conditions were the same, that is, the head-to-center position was constant at 20 mm, and the rotation speed was 4200 rpm.

The signal-to-noise ratio (SNR _m ) of the differential waveform as the output of the differential circuit was measured, and this was taken as the SNR of each magnetic recording medium. The measured signal S is an output of a linear recording density of 119 kfci and the measured noise is a root mean square value of 716 kfci. In addition, the half-width ( _dPW50 ) of the differential waveform was estimated to obtain an index used as the resolution of the recording.

Table 1 shows the average crystal grain diameter d _Mag and the standard deviation σ of the magnetic layer of each magnetic recording medium.

Table 1 magnetic recording layer Average diameter d _Mag (nm) Standard deviation σ(nm) Example 1-1 FePt 4.5 1.0 Example 1-2 CoCrPt 4.3 1.0 Example 1-3 CoPt 4.8 1.1 Example 1-4 FePd 4.8 1.3 Comparative example 1 (regular media) 7.1 2.5

Comparing the average grain diameter _dMag and the standard deviation σ of the magnetic layers of each magnetic recording medium of Example 1 and the magnetic recording medium of Comparative Example 1 in Table 1, it can be seen that each magnetic recording medium of Example 1 exhibits a smaller average The smaller average grain diameter of the deviation.

Fig. 9 shows the relationship between the amount of deposited nitrogen θ and the average magnetic grain diameter d _Mag for the Fe ₅₀ Pt ₅₀ magnetic layer obtained by nuclear reaction analysis NRA. From this figure, it can be seen that when the value of θ is 1×10 ¹³ to 1×10 ¹⁵ atoms/cm ² , crystal grains are quite small and expected. Similar results were obtained for the case of Co ₅₀ Pt ₅₀ , Fe ₅₀ Pd ₅₀ and Co ₇₀ Cr ₁₀ Pt ₂₀ magnetic layers. For each magnetic recording medium, nitrogen atoms deposited on the grain diameter control underlayer including Cu crystal grains were detected by performing chemical element distribution measurement using SIMS in the depth direction.

Fig. 10 shows the relationship between the average diameter of Cu crystal grains on the Cu layer and the average diameter of magnetic crystal grains for a Fe ₅₀ Pd ₅₀ magnetic layer having 2 x 10 ¹⁴ atoms/cm ² deposited nitrogen. As can be seen from FIG. 10, when the average crystal grain diameter of the Cu layer is 50 nm or more, the average diameter of the magnetic layer becomes sufficiently small.

11 shows the relationship between the SNR _m of each magnetic recording medium and the number of magnetic crystal grains per unit area (area density of crystal grains) n observed by TEM for the case where the average diameter d of _Cu is 100 nm. As shown in FIG. 11 , when the value of n is 1×10 ¹² to 8×10 ¹² grains/cm ² , the SNR _m increases and is expected. When the value of n is 1×10 ¹² to 8×10 ¹² grains/cm ² , on average each Cu crystal grain has a plurality of magnetic crystal grains of the magnetic recording medium.

Use the image processing and analysis software "Image-Pro Plus" (MediaCybernetics, USA) to study the ordered arrangement of magnetic crystal grains on the TEM images in each plane. Corrections were made to each TEM image to obtain patterns expressed by binary variables by increasing the contrast between regions of magnetic grains and other regions. The image represented by the binary image is then transformed with FFT. As a result, ordered arrangement of magnetic crystal grains in the magnetic layer was not observed for conventional media. On the other hand, for each magnetic recording medium having an n value of 1×10 ¹² to 8×10 ¹² grains/cm ² , orderly arrangement of magnetic crystal grains of a tetragonal lattice structure was observed.

(Example 2)

A non-magnetic 2.5-inch glass substrate was placed in a vacuum chamber, and the vacuum chamber was evacuated to 1×10 ^-6 Pa or lower. The CoZrNb soft magnetic underlayer, Cu deposition and nitrogen deposition processes were then performed using the method described in Example 1. Then a 5 nm thick (Fe ₅₀ -Pt ₅₀ )-SiO ₂ magnetic layer was formed using a (Fe ₅₀ -Pt ₅₀ )-10 mol% SiO ₂ composite target. Also, magnetic disks _having Co ₅₀ Pt 50 , Fe ₅₀ Pd ₅₀ , and Co ₇₀ Cr ₁₀ Pt ₂₀ instead of the Fe ₅₀ Pt ₅₀ layer of the magnetic disk in Example 1 were manufactured using various targets. Similarly, instead of the SiO ₂ layer in Example 1, magnetic disks were fabricated with TiO, Al ₂ O ₃ , TiC, and TaC, respectively. A carbon protective layer was then deposited and a lubricating layer was applied for each magnetic recording medium manufactured.

Table 2 shows the SNRm value and dPW ₅₀ value of each magnetic recording medium. A magnetic recording medium having a magnetic recording layer containing the compound exhibits increased SNRm and is desirable. For each compound-containing film composite, the magnetic grains of the magnetic layer were observed by TEM to be granular in structure and roughly arranged in a tetragonal arrangement.

Table 2 magnetic recording layer Signal-to-noise ratioSNRm(dB) half width dPW ₅₀ nm) Example 2-1 FePt 17.1 98 Example 2-2 CoCrPt 17.3 93 Example 2-3 CoPt 17.0 99 Example 2-4 FePd 16.8 97 Example 2-5 FePt-SiO ₂ 18.3 90 Example 2-6 CoCrPt-SiO ₂ 18.6 89 Example 2-7 CoPt- _SiO2 18.0 90 Example 2-8 FePd-SiO ₂ 18.0 89 Example 2-9 FePt-MgO 18.2 91 Example 2-10 CoCrPt-MgO 18.2 90 Example 2-11 CoPt-MgO 18.0 87 Example 2-12 FePd-MgO 17.8 86 Example 2-13 FePt-Al ₂ O ₃ 17.9 89 Example 2-14 CoCrPt-Al ₂ O ₃ 17.9 86 Example 2-15 CoPt-Al ₂ O ₃ 17.7 87 Example 2-16 FePd-Al ₂ O ₃ 17.7 89 Example 2-17 FePt-TiO 18.1 87 Example 2-18 CoCrPt-TiO 18.2 90 Example 2-19 CoPt-TiO 17.9 87 Example 2-20 FePd-TiO 17.9 88 Example 2-21 FePt-TiC 17.8 90 Example 2-22 CoCrPt-TiC 17.8 92 Example 2-23 CoPt-TiC 17.7 90 Example 2-24 FePd-TiC 17.8 88 Example 2-25 FePt-TaC 17.9 87 Example 2-26 CoCrPt-TaC 17.8 90 Example 2-27 CoPt-TaC 17.8 87 Example 2-28 FePd-TaC 17.8 88 Comparative example 2 (regular media) 15.4 109

(Example 3)

Using the process of Example 1, a 2.5-inch hard disk-like non-magnetic glass substrate was prepared and film deposition was performed until the nitrogen deposition process was completed. Then, a 10-nm-thick Pt- _SiO2 layer was deposited using the Pt-10mol% _SiO2 composite target. Various magnetic recording layers were deposited on the Pt- _SiO2 layer, and various magnetic recording media were obtained after depositing a carbon protective layer and coating a lubricating layer using the procedure described in Example 2. In addition, various composite targets were used to obtain magnetic recording media with Pd, Ir, Ag, Cu, Ru and Rh cushion layers instead of Pt cushion layers, TiO, _{Al 2 O 3} , Magnetic recording media with MgO, TiC and TaC underlayers.

Table 3 shows the SNR _m and dPW ₅₀ of various magnetic recording media having a CoCrPt-SiO ₂ magnetic recording layer and various underlayers.

table 3 Cushion Signal-to-noise ratioSNRm(dB) half width dPW ₅₀ (nm) Example 3-1 Pt-SiO ₂ 19.6 80 Example 3-2 Pd-SiO ₂ 19.6 81 Example 3-3 Ir-SiO ₂ 19.3 79 Example 3-4 Ag-SiO ₂ 19.0 78 Example 3-5 Cu-SiO ₂ 18.9 79 Example 3-6 Ru-SiO ₂ 19.8 77 Example 3-7 Rh-SiO ₂ 19.7 77 Example 3-8 Pt-MgO 19.4 81 Example 3-9 Pd-MgO 19.4 80 Example 3-10 Ir-MgO 19.0 77 Example 3-11 Ag-MgO 19.0 81 Example 3-12 Cu-MgO 19.3 81 Example 3-13 Ru-MgO 19.5 79 Example 3-14 Rh-MgO 19.5 77 Example 3-15 Pt-Al ₂ O ₃ 19.4 77 Example 3-16 Pd-Al ₂ O ₃ 19.6 82 Example 3-17 Ir-Al ₂ O ₃ 19.2 80 Example 3-18 Ag-Al ₂ O ₃ 19.4 79 Example 3-19 Cu-Al ₂ O ₃ 19.5 82 Example 3-20 Ru-Al ₂ O ₃ 19.7 75 Example 3-21 Rh-Al ₂ O ₃ 19.4 78 Example 3-22 Pt-TiO 19.6 73 Example 3-23 Pd-TiO 19.9 80 Example 3-24 Ir-TiO 19.3 78 Example 3-25 Ag-TiO 19.5 74 Example 3-26 Cu-TiO 19.0 79 Example 3-27 Ru-TiO 20.0 76 Example 3-28 Rh-TiO 19.8 78 Example 3-29 Pt-TiC 19.3 79 Example 3-30 Pd-TiC 19.3 75 Example 3-31 Ir-TiC 19.5 77 Example 3-32 Ag-TiC 19.0 78 Example 3-33 Cu-TiC 18.9 74 Example 3-34 Ru-TiC 18.9 74 Example 3-35 Rh-TiC 18.9 80 Example 3-36 Pt-TaC 19.0 79 Example 3-37 Pd-TaC 19.0 77 Example 3-38 Ir-TaC 19.3 73 Example 3-39 Ag-TaC 19.2 74 Example 3-40 Cu-TaC 19.2 78 Example 3-41 Ru-TaC 19.1 75 Example 3-42 Rh-TaC 19.1 79

It can be seen that the SNR _m of the magnetic recording media with the underlayer composite containing the compound under the CoCrPt- _SiO2 magnetic recording layer increases. Similar results were seen for magnetic recording media having other magnetic recording layers. Each magnetic recording layer and the pad layer have a granular structure, and the magnetic crystal grains are roughly arranged in a square.

(Example 4)

A 2.5-inch hard disk-shaped non-magnetic glass substrate was prepared, and the procedure was the same as in Example 3 except that an orientation control layer was provided between the soft magnetic underlayer and the grain diameter control layer. Then various magnetic recording media were obtained. As the orientation control layer, a 5 nm thick NiAl layer was deposited in an Ar atmosphere of 0.7 Pa by preparing and using a NiAl target. In addition, magnetic recording media having orientation control layers of MgO, NiO, MnAl, Ge, Si, and TiN, respectively, were produced.

Table 4 shows recording and reproducing characteristics of each magnetic recording medium having a CoCrPt-SiO ₂ magnetic recording layer and a Pt-SiO ₂ underlayer.

Table 4 Orientation Control Cushion Signal-to-noise ratioSNRm(dB) Half width DPW ₅₀ (nm) Example 4-1 none 19.8 77 Example 4-2 NiAl 20.5 76 Example 4-3 MgO 20.3 75 Example 4-4 NiO 20.0 76 Example 4-5 MnAl 20.3 77 Example 4-6 Si 20.0 73 Example 4-7 Ge 20.1 76 Example 4-8 TiN 20.4 76

As shown in Table 4, SNR _m is further increased by providing an orientation control layer. Similar results were seen for magnetic recording media with other combinations of underlayer and magnetic recording layer.

While the present invention has been described by way of its preferred embodiments, those skilled in the art will understand that various modifications can be made therein without departing from the spirit and scope of the invention.

Claims (21)

1. magnetic recording medium comprises:

Substrate;

The bed course that on above-mentioned substrate, forms;

Magnetic recording layer on the above-mentioned bed course; With

The protective seam that on above-mentioned magnetic recording layer, forms,

It is characterized in that the above-mentioned bed course that comprises the crystal grain diameter key-course comprises Cu crystal grain and the illuvium of the nitrogen-atoms that forms on above-mentioned crystal grain diameter control mat surface.

2. according to the magnetic recording medium of claim 1,

It is characterized in that it is 1 * 10 that the illuvium of above-mentioned nitrogen-atoms comprises centre plane density ¹³～1 * 10 ¹⁵Atom/cm ²Nitrogen-atoms.

3. according to the magnetic recording medium of claim 1,

It is characterized in that it is 50nm or bigger Cu crystal grain that above-mentioned crystal grain diameter control bed course comprises mean diameter.

4. according to the magnetic recording medium of claim 1,

It is characterized in that above-mentioned crystal grain diameter control bed course comprises the orientation Cu crystal grain parallel with above-mentioned substrate surface of each (100) face.

5. according to the magnetic recording medium of claim 1,

It is characterized in that it is 1 * 10 that above-mentioned magnetic recording layer comprises centre plane density ¹²～8 * 10 ¹²Crystal grain/cm ²Magnetic crystal grain, and a Cu crystal grain of above-mentioned diameter control bed course on average keeps a plurality of magnetic crystal grains.

6. according to the magnetic recording medium of claim 1,

It is characterized in that above-mentioned magnetic recording layer comprises the magnetic crystal grain of arranging with the form of tetragonal lattice structure.

7. according to the magnetic recording medium of claim 1,

It is characterized in that above-mentioned magnetic recording layer comprises the magnetic crystal grain of granular structure and surrounds the grain battery limit (BL) of each magnetic crystal grain.

8. according to the magnetic recording medium of claim 1,

It is characterized in that above-mentioned magnetic recording layer comprises the magnetic crystal grain that is selected from the alloy among Co-Cr, Co-Pt, Fe-Pt and the Fe-Pd basically and by at least a grain battery limit (BL) that constitutes that is selected from basically in oxide and the carbonide.

9. according to the magnetic recording medium of claim 1,

It is characterized in that above-mentioned magnetic recording medium is included at least one the middle bed course that is provided with between the illuvium of above-mentioned magnetic recording layer and above-mentioned nitrogen-atoms.

10. according to the magnetic recording medium of claim 9,

It is characterized in that above-mentioned middle bed course comprises at least one granular structure layer that comprises non magnetic crystal grain and surround the grain battery limit (BL) of each non magnetic crystal grain.

11. according to the magnetic recording medium of claim 10,

It is characterized in that bed course comprises the non magnetic crystal grain of at least a metal that is selected from basically among Pt, Pd, Ir, Ag, Cu, Ru and the Rh and comprises at least a grain battery limit (BL) that is selected from oxide and the nitride in the middle of the above-mentioned granular structure.

12. according to the magnetic recording medium of claim 1,

It is characterized in that above-mentioned magnetic recording medium is included in the soft magnetism bed course with soft magnetism characteristic that is provided with between above-mentioned crystal grain diameter control bed course and the above-mentioned substrate.

13. according to the magnetic recording medium of claim 1,

It is characterized in that, above-mentioned magnetic recording medium comprise between above-mentioned crystal grain diameter control bed course and above-mentioned soft magnetism bed course, have a grain orientation control bed course that is selected from least a basic chemical constitution among NiAl, MnAl, MgO, NiO, TiN, Si and the Ge basically.

14. a magnetic recording medium manufacture method may further comprise the steps:

On substrate, form the crystal grain diameter key-course that comprises Cu crystal grain;

On above-mentioned crystal grain diameter control mat surface, form the illuvium of the nitrogen-atoms of deposit nitrogen; With

On the substrate of crystal grain diameter control bed course, form magnetic recording layer with above-mentioned deposit nitrogen layer.

15. according to the magnetic recording medium manufacture method of claim 14,

It is characterized in that in the step of the illuvium of above-mentioned formation nitrogen-atoms, deposit centre plane density is 1 * 10 on above-mentioned crystal grain diameter control mat surface ¹³～1 * 10 ¹⁵Atom/cm ²Nitrogen-atoms.

16. according to the magnetic recording medium manufacture method of claim 14,

It is characterized in that, in the step of above-mentioned formation crystal grain diameter control bed course, form the above-mentioned crystal grain diameter control bed course that comprises 50nm or bigger Cu crystal grain, and, in the step of the illuvium of above-mentioned formation nitrogen-atoms, the above-mentioned nitrogen-atoms of deposit on above-mentioned crystal grain diameter control mat surface.

17. according to the magnetic recording medium manufacture method of claim 14,

It is characterized in that in the step of above-mentioned formation crystal grain diameter key-course, the orientation above-mentioned crystal grain diameter parallel with above-mentioned substrate surface that forms (100) face of crystal grain controlled the above-mentioned Cu crystal grain of bed course.

18. according to the magnetic recording medium manufacture method of claim 17,

It is characterized in that, in the step of above-mentioned formation magnetic recording layer, in above-mentioned magnetic recording aspect, arrange above-mentioned magnetic crystal grain with the form of tetragonal lattice structure basically.

19. according to the magnetic recording medium manufacture method of claim 14,

It is characterized in that in the step of above-mentioned formation magnetic recording layer, forming centre plane density is 1 * 10 ¹²～8 * 10 ¹²Crystal grain/cm ²Above-mentioned magnetic recording layer in above-mentioned magnetic crystal grain.

20. magnetic recording and transcriber comprise:

The magnetic recording medium of the protective seam that comprises substrate, the magnetic recording layer on the bed course that forms on the above-mentioned substrate, above-mentioned bed course and on above-mentioned magnetic recording layer, form; wherein; described bed course comprises the illuvium of crystal grain diameter control bed course that contains Cu crystal grain and the nitrogen-atoms that forms on above-mentioned crystal grain diameter control bed course

Be used to drive the recording medium driving mechanism of above-mentioned magnetic recording medium;

Be used to record information on the above-mentioned magnetic recording medium and the record and the reproducing head mechanism of information reproduction from the above-mentioned magnetic recording medium;

Be used to drive the magnetic head driving mechanism of above-mentioned record and reproducing head; With

Be used to handle the record and the reproducing signal disposal system of tracer signal and reproducing signal.

21. according to the magnetic recording and the transcriber of claim 20,

It is characterized in that above-mentioned record and reproducing head mechanism comprise single-pole-piece magnetic head.

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